Process and apparatus for spray coating



Feb. 4, 1930. RDARUNG 1,746,228

PROCESS AND APPARATUS FOR SPRAY COATING Filed Jan. 24, 1927 2Sheets-Sheet 1 i L h: 5 ml w 50 ii 1 I 14. H

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INVENPOR,

ATTORNEYS.

Feb.,4, 1930. H. R. DARLING PROCESS AND APPARATUS FOR SPRAY COATINGFiled Jan. 24, 1927 2 Sheets-Sheet 2 INVENT y Rpm .0 1 1 M Q IATTORNEYS.

72 174 75 HcLTT Patented Feb. '4, 1930 4 HARRY R. DARLING, OF BOGHESTER,NEW YORK PROCESS AND APPARATUS FOR SPRAY GOATING Application filedJanuary 24, 1927. Serial No. 162,985.

This invention relates to coating machines,.

particularly to spray-coating machines and to a process by which suchcoating can be economically and safely carried out. One object of myinvention is to provide an apparatus for. spraying articles in which theunused spray is recovered. Anotherobject is to provide an apparatus forkeeping the coating composition properly mixed in condition for use.Another object is to provide for conditioning the coating material byconstant circulation. Another object is to provide a process of coatingin which unused spray coating is entrapped in a body of the coating 1composition, and other objects will appear from the followingspecification, the novel features being particularly pointed out in theclaims at the end thereof.

It is common practice to coat articles by spraying with a. suitablecoating material which usually contains an organic liquid, and the wastespray, that is the spray which does not adhere to the article beingcoated usually passes into a hood from which the spray laden air isevacuated. This is necessary to protect the workman. A large lossresults, however, from such practice, since frequently only a smallpercentage of the total spray coating adheres to the article he ingcoated and consequently a large part of the spray is lost. 1 Thisinvention not only recovers the waste I spray in -a flow of coatingcompositionbut also leaves less impurities in the form of sprayedparticles and volatile solvents in the hood to be removed by theventilating sys form of plate for supporting a curtain of coatingcomposition,

Fig. 5 is a perspective view of a work holding tray adapted for use withthe coating machine, and i Fig. 6 is a diagrammatic view, partly frontelevation and partly section of a battery of coating machines showinganother embodiment of my invention.

As an example of my invention, I have shown a typical spraying hood 1comprising a body portion 2, spraying opening 3 and a tapering top 4from which the vent pipe 5 leads to a suitable air evacuating mechanismof any standard type. The apparatus may rest on a table 6 supported onlegs 7.

Coming now to my invention, I provide a supply. tank 10 for a coatingcomposition containing an organic liquid, which coating composition maybe of any well known type. Tank 10 is preferably raised above the workopening 3 in hood 1 and may be supported on a bracket 11.

From tank 10 I provide a supply system divided into-two parts. One partincludes a pipe 12 having a valve 13 and a distributing head. 14, thislatter part here consisting of a pipe 15 having spaced apertures 16. Theother part consists of a pipe 17 which is preferably flexible,supporting a spraying head, preferably a well known type of spray gun18. A valve 19 controls the flow of coating composition. I

An angularly disposed plate 20 is mounted in the hood and this plate mayhave sides 21 and a top 22, the distributing head 14 lying near the top22. When valve 13 is opened the coating composition will flow throughapertures 16 down plate 20 thus forming a curtain C towards which thespray from gun 18 is directed. The flow may be controlled by valve 13 sothat an even film or curtain of composition covers plate 20.

A recovery system is employed. A tray 25 receives the flow of coatingcomposition from plate 20 and the bottom 26 is slanting towards a drainpipe 27 so that the composition may be again used. I prefer to havedrain pipe 27 lead-to a pump 28 so that the recovered material will bereturned to the supply tank -through pipe 29, filter 30 and pipe 31,since this not only replenishes tank 10 but keeps the coatingcomposition continuously a itated by circulating through the systems aove described and thus keeps the composition in ideal condition for use.

Referring to Fig. 3, it will be noted that the work W received only acomparatively small amount of the spray S directed towards it, and thatthe spray which does not adhere to the work, the waste spray, passes onand is entrapped in the curtain C of coating composition flowing downplate 20. By thus converting the spray back into the stream of coatingcomposition, much less volatile solvent is released than is usually thecase and practically none of the waste spray is carried from the hoodthrough -vent 5, because the spray is projected with considerable forcefrom gun 18 and quickly travels the short distance from the gun to thecurtain. Thus much less evacuating power is required and the workman iscorrespondingly more fully protected from inhaling coating compositionladen air.

Additional material may be added to tank 10 to replenish the supply ofcoating composition, and when necessary a volatile solvent may be addedto reduce the viscosity of the composition. The short travel of the sprabefore it again is converted from finely divi ed droplets into thestream of coating composition, greatl lessens the surface exposed to theair an consequently the loss of volatile solvents is small. One skilledin the art can easily regulate the supply of coating composition toproduce the best results for the wor at hand. e

In the first three fi ures the plate is mounted at a considera le angleto. the top 6 of the bench so that the curtain C which flows over plate20 forms a target against which the spray S is directed when work W isheld in front of the curtain. In Fig. 4 I have" illustrated another typeof angularly disposed plate 40 which is particularly suitable for somety es of work. Here the plate ma be provided with sides 31 and ends 32.distributing head 33 may consist of a pipe 34 having a series ofapertures 35 through which the coating composition may pass so that itmay flow in a curtain .0 across the plate 30. An inlet pipe 36 suppliespipe 34 at one end, at the opposite end of plate 30 there is an exitpipe 37. The plate 30 is mounted at an angle to the table top 6 restingon the block 38 atone end and a wedge 39 at the other, the inclinationof the wedge being just suflicient to direct the coating composit1on ina smooth even flow across plate 30 to theexit pipe 37.

Ipre'ferably provide a basket mount such as a post 40 which may besupported by the plate 30 in position to receive a coupling 41 i on thebottom of a wire basket 42 which may be of any well known constructionand which may support small pieces of work Wa. When spraying smallpieces of work the spray is generally directed downwardly so that theunused spray passes through the wire mesh 43 of the basket and becomesentrapped in the curtain C.

So far I have described a typical spraying machine as consisting of asingle unit. I

generally find, however, that it is preferable to provide a series ofspraying units, as shown in Fig. 6, for this leads to certain economies;particularly facilitating cleaning, as will be hereinafter described.

In Fig. 6 there is shown a series of spraying cabinets 1 having theusual air exhaust pipes 5 leading to a main exhausting line 55. Thesecabinets are substantially alike, althrough I have here shown two of thecabinets as being provided with a circular opening 56 and two with asquare front opening 57; the former type is useful when the curtain C ismade to flow over an angularly disposed plate 20 which is mounted toreceive spray directed substantially horizontally, while the latter typeof opening 57 is chiefly used where the angularly disposed plate 30 ismounted to receive spray directed more nearly in a vertical direction.For the first two hoods the distributing heads 14 are similar to thosedescribed above in detail referring to Figs. 1 to 3 inclusive, and inthe second two illustrated hoods the sprinkling heads 33 are similar tothose described with special reference to Fig. 4.

The piping of the multiple system will now be described. A supply tank60 is provided, and from this tank a pipe line 61 leads downwardly,being broken by a valve 62. From pipe line 61 lines 63 extend to eachside to supply through pipes 64 the air brush lines 65. Valves 66control the entrance of coating composition to pipe lines 64, andfaucets 19 control the entrance of coating composition to the flexibleconnections 17 which lead to the air brushes 18.

- A second coating composition supply line 67 leads from pipes 61 topipes 68, thus farnishing coating composition to the spraying heads 14and 33, the individual spraying heads being controlled by valves 69.After the curtain C flows over the angularly disposed plates, theexhaust pipes 27 and 37 collect the coatin composition which then flowsthrough pipes 0 to a pipe 71. which leads into a tank 72 divided intotwo parts, the upper part 73 carrying a screen 74 which filters thecollected coating composition which flowsthrough into section 75 fromwhich a pipe 76 leads to a power pump 7 7.- Pump 77 directs the coatingmaterial through pipe 78 past valve 7 9 into the top 80 of tank 60. v

It will be noted that pipe 78 is connected to pipe 61 b means of a pipe81 in which there is a va ve 82 which is normally closed.

With the parts as a ove described, there is to time byreplenishing thesupply intank 60 or filter tank 72.

Usually it is necessary to add .to tank 72 small quantities of avolatile solvent from time to time, and to occasionally replenish thesupply of coating composition therein. I find, however, that withsprayingcabinets,

.as above described, there is a much less loss of volatile solvents thanis usually the case, because, on account of the short travel of thespray'before it becomes entrapped in the curtain, the finely divideddroplets are not carried off through the vent pipes 5 in largequantities. I have found it possible to reduce the flow of air throughthe vent pipes approximately 90%, (although it is to be understood thatthis and the following figures are given by way of illustration only)over the usual hood wherein the unused spray is carried out by theexhaust.

By thus reducing the quantity of exhausted air, the quality of the Workhas been increased, so that for certain classes of Work the rejects havebeen around 3% where with the old type of machines about 15% of the Workwas rejected. This improvement may be due to the fact that where a muchgreater air evacuation was necessary for the old type hoods, the dirtand dust from the floor and in the spraying room were drawn into thehoods through the openings in which the Work being sprayed was held, sothat foreign matter. was thus accumulated while spraying process wasgoing on.

I have found that with the curtain equipped spraying hoods that the airpipes 15 do not require to be cleaned every six or eight weeks as wasprev ously required where the hoods were not equipped with suchcurtains. Since the quantityof coating which passes up into pipes 5 ispractically negligible with the curtain equipped machines, the pipes 5need to be cleaned only at very infrequent intervals.

With the pipe arranged as above described with reference to Fig. 6, thecleaning operation may be easily performed as follows:

After the days work is over the supply of coating composition from theair guns 18 is cut off by turning the faucets 19, and if desired, thevalve 66 may also be turned to prevent further flow of coatingcomposition into pipe 64, valve 62 is also turned off preventing furtherflow of coating composition into pipes 67 and 68, the valve 69 beingleft open so that the remaining coating composition may passfrom pipes68 and will become exhausted, flowing over the angularly disposedplates-20 and 30. After the coating composition has passed from theseplates through pipes 70 and 71 through basket 72, the pump 77 continuesto operate until the coating composition in compartment 75 is exhaustedbepump 77 is again set in motion and the cleaning fluid is circulatedthrough pipes 78,

81, 67 and 68, distributing heads 14 and 33,

draining pipes 37 and 27 and thence to tank 72 through pipe 71. When theparts have thus been cleaned, valve 83 may be opened and valve 84 may beclosed so that the cleaning fluid may be drawn off through pipe-85.During the cleaning operation the pipes 64 and 65 remain vfull of thecoating composition, since no air can come in contact with the coatingcomposition it will remain in workable condition for considerable time.At the infrequent occasions when it is necessary to clean these pipes,the supplv tank may be filled with cleaning fluid which may becirculatedthrough the various lines.

While I have described preferred embodiments of my invention, obviouslynumerous difierent arrangements of parts can be made without departingfrom the scope of my invention, and I claim as within the scope thereofall such embodiments as may come within the terms of the followingclaims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In a coating apparatus, a supply tank for coating composition, anangularly disposed plate, a pipe for supplying coating composition tothe plate over which it may flow in a curtain, a pipe leading to aspraying head adapted to be directed towards the curtain whereby wastespray not adhering to an article being sprayed may be entrapped by thecomposition flowing over the angularly disposed plate.

2. In a coating apparatus, the combination with an angularly disposedmember, ofa distributing member mounted to deliver a curtain of coatingcomposition along the top thereof, a source of supply of coatingcomposition, connections between the supply and distributing member, aspraying'head, connections between the supply and the spraying head,said spraying head being adapted to direct a spray against an articleheld between said head and said curtain whereby wva'ste spray may becomeentrapped by said curtain, means for collecting the coating com-- lotpositions, connections between the supply and distributing member, aspraying head, connections between the supply and the spraying head,said spraying head being ada ted to direct a spra against an article helbetween said hea and said curtain whereby waste spray may becomeentrapped 5 by said curtain, and means for returning the coatingcomposition flowing from the curtain and containing said waste spray tothe source of supply.

4. n a coatin a paratus, the combination with an angular y isposedmember, of a distributing member mounted to deliver a curtain of coatingcomposition along the top thereof, a source of supply of coatingcomposition, connections between the supply and distributing member, aspraying head, connections between the supply and the spraying head,said spraying head being adapted to direct a s ray against an articleheld between said head and said curtain whereby waste spray may becomeentrapped by said curtain,

and means for collecting the coating composition flowing from saidcurtain containing wastespray, means for agitating the coatingcomposition including a pump, and connections between said pump, coatingcomposition collecting means and source of supply through which saidpump may deliver the collected coating composition to the source of pp y5. n a coating a paratus, the combination with a hood, 0 an angularlydisposed plate therein, a source of coating composition, a pipe leadingfrom said source to said plate adapted to furnish coating composition toflow over said plate in a curtain, a spraying head adapted to face saidplate, a pipe connecting said source of supply and said spraying head,whereby an article held in front of said curtain may be sprayed, thewaste s ray being entrapped by said curtain, and a rain alon an edge ofsaid angularly disposed plate a apted to collect said coatingcomposition.

6. In a coating a paratus, the combina tion with a hood, 0 an angularlydisposed plate therein, a source of coating composition, a pipe leadinfrom said source to said plate adapted to urnish coating composition toflow over said plate in a curtain, a spraying' head adapted to face saidplate, a pipe connecting said source of supply and said spraying head,whereby an article held in front of said curtain may be sprayed, thewaste spray being entrapped by said curtain, a drain, a return systemfor carrying said coating composition collected by the drain into thesource of supply.

7. In a spray coating, machine, the combination of a spraying chamber, asource of coating materlal, an angularly disposed plate adapted tosupport a curtain of coating comsystem adapted to deliver the coatingcomposition from the spray and curtain to the source of materials and aby-pass and valve system connected to the supply and return pipesadapted to cut off the supply tank, permitting cleaning fluid to 'becirculated through parts of the return and supply system.

8. In a spray coating machine, the combination of a spraying chamber, asource of coating material, an angularly disposed plate adapted tosupport a curtain of coating composition, a spraying head, separatesupply lines leading to the spraying head and plate, valves forcontrollin the flow of coating composition to these lines, a returnpiping system adapted to deliver the coating com- "position from thespray and curtain to the source of materials and a by-pass and valvesystem connected to the supply between the spraying head and the curtainand to the return pipe whereby the tank and spraying head may be cut offand the remainder of the system may be flushed out for cleaning.

9. In a spraying machine, the combination witha plurality of sprayingchambers, of a tank adapted to contain a su ply of coating'composition,an angularly isposed plate in each chamber, a pipe line connected to thetank adapted to supply coating com position to the angularly disposedplates, a spraying head for each chamber, a pipe line adapted to supplyeach spraying head, said pipe line being connected to said tank, valvesfor independently permitting a flow of coating composition in the twopipe lines, a return pipe line adapted to deliver coating compositionfrom the spraying head and the angularly disposed plate to the supplytank, a filterbeing located in the return line, and a by-pass locatedbetween the two supply ipe lines and the return pipe whereby cleaningcomposition may be flowed through one of the supply systems.

Signed at Rochester, New York, this 20th .day of January, 1927.

HARRY R. DARLING.

position, a spraying head, separate supply lines leading to the sprayinghead and plate, valves for controlling the flow of coating compositionto these 1 nes, a return piping

